it is overrated at the amateur levels up to 5.0. i play with many of these wannabes and topspin junkies types and their topspin are pretty weak. the ball just bounces high but has little pace. they are easier to handle than backspin slices for me. you can break them down pretty easily by just moving them around, hitting on the rise, throw in some slices and short balls, and not give them time to recover and set up.

but topspin at the ATP level is totally different obviously there is a ton of pace mixed in with ridiculous amounts of topspin. so players can still keep the ball inside even with big swings at the ball for crazy passing shots and create insane angles. but guys like nadal use way too much topspin it should be illegal lol

Good observation. Most club level topspin (adults) is ineffective, other than the fact that it helps keep the ball in. Seasoned clubbies have no problem dealing with it, though you can get away with those guys who only play with flat-hitting people.